A federal intelligence court, in a rare public opinion, issued a major ruling validating the power of the president and Congress to wiretap international phone calls and intercept e-mail messages without a specific court order, even when Americans’ private communications may be involved.

The court decision, made in August 2008 by the Foreign Intelligence Surveillance Court of Review, came in an unclassified, redacted form.

The decision marks the first time since the disclosure of the National Security Agency’s warrantless eavesdropping program three years ago that an appellate court has addressed the constitutionality of the federal government’s wiretapping powers. In validating the government’s wide authority to collect foreign intelligence, it may offer legal credence to the Bush administration’s repeated assertions that the president has the power to act without specific court approval in ordering national security eavesdropping that may involve Americans.

The Aug. 22 appeals court decision upheld a secret ruling issued last year by the intelligence court that it oversees, known as the Foreign Intelligence Surveillance, or FISA, court. In that initial opinion, the secret court found that Congress had acted within its authority in August 2007 when it passed a hotly debated law known as the Protect America Act, which gave the executive branch broad power to eavesdrop on international communications.

“The Department of Justice is pleased with this important ruling by the Foreign Intelligence Surveillance Court of Review, which upholds the constitutionality of foreign intelligence surveillance conducted under the Protect America Act of 2007,” a Justice Department statement said.

The court ruling grew out of a previously undisclosed challenge from a telecommunications provider, which questioned the constitutional authority of the executive branch in ordering it to capture and turn over international communications without court approval.

The telecommunications company, which was not identified, refused to comply and instead challenged its legal basis under the 2007 law.

The FISA court rejected the telecommunication companies’ challenge. It found that the Protect America Act did not violate the Constitution because the Fourth Amendment, which prohibits unreasonable searches and seizures, contained an exception for the collection of foreign intelligence information.

The opinion did not directly rule on the legality of the once-secret operation authorized by President Bush between October 2001 and early 2007, which allowed the National Security Agency to eavesdrop on the international communications of Americans suspected of ties to terrorists. The disclosure of the program’s existence in The New York Times in December 2005 set off a national debate on wiretapping, privacy and the limits of presidential power. Critics charged that Mr. Bush had violated a 1978 law requiring that the government obtain a court order to listen in on Americans’ communications.